package 第六章面向对象;

//测试顾客
public class OOtest05 {
    public static void main(String[] args) {
        Customer c = new Customer();
        System.out.println(c.id);

        c.id = 9999;
        // c=null;   java.lang.NullPointerException空值异常 空引用访问实例相关的数据
        System.out.println(c.id);

    }
}
